An integrated system and method for recovering carbon from liquid ammonia based on membrane distillation

Abstract

The present invention discloses an integrated system and method for recovering carbon fixation from ammonia liquid based on membrane distillation, comprising: a biogas tank; a direct contact membrane distillation structure, comprising a permeate channel, a feed liquid channel connected to the biogas tank, and a membrane assembly arranged between the permeate channel and the feed liquid channel; a temperature control device, used to control the temperature difference on both sides of the membrane assembly; a gas channel, a microporous hollow fiber membrane is arranged between the gas channel and the permeate channel; a biogas tank, connected to the gas channel; and a methane detection device. The ammonia liquid in the biogas is concentrated to absorb carbon dioxide in the biogas, and the reaction product can be used to produce ammonium nitrogen fertilizer. The methane concentration in the purified biogas meets the standard and can be added to the pipeline network as biogas or used for gas turbine power generation. The integrated system realizes the resource utilization of waste in the process of organic sewage treatment and reduces energy consumption and carbon emission costs, which has important economic benefits and environmental and social values.

Description

Technical Field

[0001] The present invention relates to the technical field of green energy application, and in particular to an integrated system and method for recovering carbon from liquid ammonia based on membrane distillation. Background Art

[0002] In recent years, with the rapid development of my country's economy and the acceleration of industrialization, the total carbon emissions have continued to grow. At present, the carbon emissions of my country's sewage treatment industry account for about 1% of the total emissions of the whole society, which is the largest proportion in the environmental protection industry. Therefore, sewage treatment is one of the key areas of carbon reduction. To this end, the sewage treatment industry is actively seeking new methods for the utilization of organic sewage and carbon fixation and emission reduction.

[0003] At present, the traditional sewage treatment mode is to exchange energy consumption for water quality from the perspective of energy conversion. In order to reduce water pollution, a large amount of electricity is used, which indirectly leads to the generation of a large amount of CO2. At the same time, the process of organic sewage treatment requires a large amount of fuel and reagents, which also indirectly leads to the emission of a large amount of greenhouse gases. The anaerobic sewage treatment process and the anaerobic sludge digestion process will produce a large amount of biogas. Direct emission will cause a more serious "greenhouse effect", but the high content of CO2 in biogas also limits the deep utilization of biogas. The existing separation technology of CO2 in biogas can be divided into physical technology, chemical technology and biological technology, including membrane separation, water washing, pressure swing adsorption, low temperature separation, chemical absorption and other technologies. Among them, chemical absorption is the most mature technology currently used in biogas purification engineering, but the evaporation stage in the chemical adsorption reaction process will lose part of the solvent, and the regeneration stage requires a lot of energy.

[0004] As a byproduct of biogas production, biogas slurry contains high levels of nutrients, especially high concentrations of ammonia nitrogen. Direct application in agricultural production may lead to serious environmental problems, such as eutrophication of water bodies. In addition, due to the high solubility of ammonia in water, a small amount of ammonia will cause a sharp deterioration of the aquatic environment and cause considerable harm to water resources. Therefore, how to efficiently recover ammonia in biogas slurry and effectively reduce the CO2 concentration in biogas is the key to achieving waste resource utilization and carbon fixation and emission reduction in the current sewage treatment industry.

[0005] In view of this, it is necessary to design an integrated system and method for ammonia liquid recovery and carbon fixation based on membrane distillation to solve the above problems. Summary of the invention

[0006] The object of the present invention is to provide an integrated system and method for recovering ammonia and fixing carbon based on membrane distillation, which can simultaneously realize the dual functions of recovering ammonia in biogas and capturing carbon dioxide in biogas, and can be used to purify biogas to prepare biogas and use the reaction products for fertilizer production.

[0007] To achieve the above-mentioned purpose of the invention, the present invention provides an integrated system for recovering carbon from liquid ammonia based on membrane distillation, comprising:

[0008] A biogas slurry tank, used for storing biogas slurry;

[0009] A direct contact membrane distillation structure, comprising a permeate channel, a feed liquid channel connected to the biogas slurry tank, and a membrane assembly arranged between the permeate channel and the feed liquid channel;

[0010] Temperature control equipment, used to control the temperature difference on both sides of the membrane module;

[0011] a gas channel, wherein a microporous hollow fiber membrane is disposed between the gas channel and the permeate channel, so that the gas channel, the microporous hollow fiber membrane and the permeate channel together form a gas separation structure that utilizes the liquid continuously enriched in the permeate channel as a carbon dioxide absorbent;

[0012] A biogas tank connected to the gas channel;

[0013] The methane detection device is used to detect the methane purity in the clean biogas output through the gas channel.

[0014] As a further improvement of the present invention, a first suction pump is provided on the permeate channel to circulate the liquid in the permeate channel.

[0015] As a further improvement of the present invention, the gas channel outlet is connected to its inlet to form a gas circulation processing passage.

[0016] As a further improvement of the present invention, the membrane assembly and the microporous hollow fiber membrane are both polytetrafluoroethylene membranes with a membrane pore size of 0.22-5 μm.

[0017] As a further improvement of the present invention, the temperature control device comprises a heating device for heating the biogas slurry and a cooling device for reducing the temperature of the permeate.

[0018] A treatment method for an integrated system for recovering and fixing carbon from ammonia liquid based on membrane distillation comprises the following steps:

[0019] S1. The biogas slurry in the biogas slurry tank is fed into the feed liquid channel of the direct contact membrane distillation structure, so that under the action of the vapor pressure difference, the water vapor and ammonia gas in the biogas slurry pass through the membrane assembly into the permeate channel to be enriched to form ammonia liquid;

[0020] S2, sending biogas into the gas channel, allowing carbon dioxide in the biogas to enter the permeate channel through the microporous hollow fiber membrane, and using the ammonia liquid in step S1 to absorb carbon dioxide in the biogas;

[0021] S3. Use a methane detection device to detect the methane purity in the clean biogas output from the gas output channel. If the methane purity is less than a certain value, the clean biogas is allowed to enter the gas channel again for processing; if the methane purity is greater than or equal to a certain value, the clean biogas is stored.

[0022] As a further improvement of the present invention, the flow directions of the ammonia liquid in the permeate channel and the biogas in the gas channel are opposite to each other, so that the ammonia liquid and the biogas are subjected to cross-flow absorption.

[0023] As a further improvement of the present invention, the relationship between the purity of methane in the clean biogas and the temperature difference between the two sides of the membrane module and the biogas flow rate is as follows:

[0024] P=(0.5543+0.0054*T+0.001699*V)*100

[0025] Wherein, P is the methane content in the clean biogas, %; T is the temperature difference between the two sides of the membrane module, °C; V is the biogas flow rate, mL / min.

[0026] As a further improvement of the present invention, the ammonia concentration in the biogas slurry is 0.4-1 mol / L.

[0027] As a further improvement of the present invention, the ammonia liquid circulates in the permeate channel, and the flow rate of the ammonia liquid is 0.5-2 L / min.

[0028] The beneficial effects of the present invention are:

[0029] 1. The present invention sequentially arranges a feed liquid channel, a permeate channel and a gas channel, and uses the permeate channel as both an ammonia liquid enrichment channel and a reaction channel for ammonia liquid and carbon dioxide. The ammonia liquid in the permeate channel can be continuously enriched by membrane distillation, so that during the carbon dioxide absorption process, the ammonia liquid concentration is always maintained at a relatively high level, so that the carbon dioxide absorption process can be quickly completed by using high-concentration ammonia liquid, and the carbon dioxide concentration in the biogas can be effectively reduced.

[0030] 2. The integrated system for ammonia liquid recovery and carbon fixation based on membrane distillation of the present invention has a simple structure. By adopting a method of simultaneous ammonia liquid enrichment and carbon dioxide absorption, it can effectively reduce the ammonia liquid recovery and carbon dioxide treatment time and reduce the treatment time cost of the sewage treatment plant.

[0031] 3. The present invention uses biogas and sludge obtained after biological treatment of organic sewage as raw materials, and concentrates ammonia in the biogas to absorb carbon dioxide in the biogas. The reaction product can be used to produce ammonium nitrogen fertilizer. The methane concentration in the purified biogas meets the standard and can be added to the pipeline network as biogas or used for gas turbine power generation. The integrated system realizes the resource utilization of waste in the process of organic sewage treatment and reduces energy consumption and carbon emission costs, which has important economic benefits, environmental protection and social value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure of the integrated system for ammonia liquid recovery and carbon fixation based on membrane distillation.

[0033] Reference numerals

[0034] 10. Biogas slurry tank; 21. Feed liquid channel; 22. Permeate channel; 23. Membrane assembly; 241. First suction pump; 242. Second suction pump; 25. Heating device; 26. Cooling device; 27. Ammonium bicarbonate detection device; 31. Gas channel; 32. Microporous hollow fiber membrane; 33. Air pump; 341. Pickling equipment; 342. Methane detection device; 35. Methane storage tank; 36. Biogas tank. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0037] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0038] like Figure 1 As shown, the present invention provides an integrated system for recovering carbon from ammonia liquid based on membrane distillation, comprising:

[0039] A biogas slurry tank 10, used for storing biogas slurry;

[0040] A direct contact membrane distillation structure, comprising a permeate channel 22, a feed liquid channel 21 connected to the biogas slurry tank 10, and a membrane assembly 23 disposed between the permeate channel 22 and the feed liquid channel 21;

[0041] Temperature control equipment, including a heating device 25 for heating the biogas slurry and a cooling device 26 for reducing the temperature of the permeate;

[0042] A gas channel 31, wherein a microporous hollow fiber membrane 32 is disposed between the gas channel 31 and the permeate channel 22, so that the gas channel 31, the microporous hollow fiber membrane 32 and the permeate channel 22 together form a gas separation structure that utilizes the liquid continuously enriched in the permeate channel 22 as a carbon dioxide absorbent;

[0043] A biogas tank 36 connected to the gas channel 31;

[0044] The methane detection device 342 is used to detect the methane purity in the clean biogas output through the gas channel 31 .

[0045] The permeate channel 22 of the direct contact membrane distillation structure is filled with condensed water; the heating device 25 heats the biogas slurry, and the cooling device 26 maintains the condensed water at a relatively low temperature, so that a temperature difference is formed on both sides of the membrane assembly 23, and then under the action of the vapor pressure difference, the water vapor and ammonia in the biogas slurry volatilize and penetrate through the membrane pores of the membrane assembly 23 into the condensed water in the permeate channel 22. As the membrane distillation proceeds, the ammonia content in the condensed water gradually increases, that is, the ammonia liquid is continuously enriched in the permeate channel 22; the microporous hollow fiber membrane 32 can allow biogas to penetrate into the permeate channel 22, and at the same time isolate the ammonia liquid to prevent the ammonia liquid from entering the gas channel 31. When the biogas enters the gas channel 31, the carbon dioxide in the biogas enters the permeate channel 22 through the microporous hollow fiber membrane 32 and is absorbed by the ammonia liquid. The methane in the biogas is insoluble in water and flows out along the gas channel 31, that is, clean biogas with a low carbon dioxide content is output at the outlet of the gas channel 31.

[0046] Specifically, flow controllers (not shown) are provided on the feed liquid channel 21, the permeate channel 22 and the gas channel 31, respectively. Since the temperature difference is a key parameter affecting the ammonia liquid enrichment rate in the direct contact membrane distillation structure, and the biogas flow rate significantly affects the effect of carbon dioxide entering the permeate channel 22 through the microporous hollow fiber membrane 32 and being absorbed by the ammonia liquid, the present invention can match the ammonia liquid enrichment rate in the permeate channel 22 with the carbon dioxide absorption rate by controlling the temperature difference and biogas flow rate on both sides of the membrane assembly 23, so as to maximize the carbon dioxide absorption efficiency, so as to quickly reduce the carbon dioxide content in the biogas while achieving the best economic benefits. The reaction product of ammonia liquid and CO2 can be used as fertilizer for agricultural production after concentration and post-treatment, and has certain economic value.

[0047] By arranging ammonia liquid enrichment and carbon dioxide absorption in the same channel, namely the permeate channel 22, it is possible to use membrane distillation to replenish ammonia liquid while carbon dioxide reacts with ammonia liquid to reduce the ammonia liquid concentration based on membrane distillation technology. That is, the characteristic of ammonia liquid that can be continuously enriched during the membrane distillation process is utilized to avoid the concentration of ammonia liquid used to treat carbon dioxide decreasing with the extension of treatment time, thereby affecting the absorption effect of carbon dioxide, thereby effectively reducing the carbon dioxide concentration in the biogas while efficiently recovering the ammonia liquid in the biogas.

[0048] Specifically, a first suction pump 241 is provided on the permeate channel 22 , and the inlet of the permeate channel 22 is connected to the outlet thereof, so that under the action of the first suction pump 241 , the ammonia liquid circulates in the permeate channel 22 .

[0049] Specifically, the temperature reduction device 26 is a low-temperature constant temperature device connected to the permeate channel 22 to reduce the temperature of the ammonia liquid in the permeate channel 22 .

[0050] The permeate channel 22 is also connected to an ammonium bicarbonate detection device 27. When the ammonium bicarbonate content in the permeate channel 22 exceeds a certain value, the liquid in the permeate channel 22 is discharged and replaced with new condensed water to continue circulating for ammonia enrichment and carbon dioxide absorption.

[0051] Specifically, a second suction pump 242 is provided on the feed liquid channel 21; the heating device 25 is arranged between the biogas slurry tank 10 and the inlet of the feed liquid channel 21, so that under the action of the second suction pump 242, the biogas slurry flows out of the biogas slurry tank 10, flows into the feed liquid channel 21 after being heated by the heating device 25, and after being treated by membrane distillation, the biogas slurry flows into the biogas slurry tank 10 through the outlet of the feed liquid channel 21, thereby realizing the circulation of the biogas slurry.

[0052] Specifically, the gas channel 31 is connected to an air pump 33, and the outlet of the gas channel 31 is connected to the inlet thereof, forming a gas circulation processing passage.

[0053] A methane detection branch and a methane storage branch are provided on the gas circulation treatment passage. A methane storage tank 35 is provided on the methane storage branch. A pickling device 341 and a methane detection device 342 are sequentially provided on the methane detection branch along the gas flow direction. Exemplarily, the acid in the pickling device 341 is dilute sulfuric acid with a mass fraction of 50%; under the action of the air pump 33, the biogas enters the gas channel 31 from the biogas tank 36 for treatment, and is then output through the outlet of the gas channel 31. The methane content in the clean biogas is detected by the methane detection device 342. When the methane detection device 342 detects that the methane purity in the clean biogas output through the gas channel 31 is lower than a certain value, the clean biogas is allowed to enter the gas channel 31 again, and the ammonia liquid in the permeate channel 22 is used for carbon dioxide reabsorption treatment; when it is detected that the methane content in the clean biogas is higher than a certain value, the clean biogas is input into the methane storage tank 35.

[0054] Regarding the detection of the content of methane in the clean biogas, it can be set to real-time detection as needed, or it can be set to interval detection. In this embodiment, the methane detection device 342 is a gas chromatograph.

[0055] Specifically, corresponding valve controllers may be provided according to actual control requirements to achieve control of each channel and passage.

[0056] Specifically, the membrane assembly 23 and the microporous hollow fiber membrane 32 are both polytetrafluoroethylene membranes with a pore size of 0.22-5 μm. The surfaces of the polytetrafluoroethylene membranes are hydrophobized on both sides to prepare a super-hydrophobic nanowire coating, maintaining a contact angle greater than 150° and a sliding angle less than 10°.

[0057] The whole system is sealed by sealing adhesive and rubber ring, wherein the rubber ring is made of fluororubber.

[0058] The present invention also provides a treatment method of an integrated system for recovering and fixing carbon from ammonia liquid based on membrane distillation, comprising the following steps:

[0059] S1, feeding the biogas slurry in the biogas slurry tank 10 into the feed liquid channel 21 of the direct contact membrane distillation structure, so that under the action of the vapor pressure difference, the water vapor and ammonia gas in the biogas slurry pass through the membrane assembly 23 and enter the permeate channel 22 to be enriched to form ammonia liquid;

[0060] S2, sending the biogas into the gas channel 31, allowing the carbon dioxide in the biogas to enter the permeate channel 22 through the microporous hollow fiber membrane 32, and using the ammonia liquid in step S1 to absorb the carbon dioxide in the biogas;

[0061] S3. Use the methane detection device 342 to detect the methane purity in the clean biogas output from the gas output channel. If the methane purity is less than 90% VOL, the clean biogas is allowed to enter the gas channel 31 again for processing; if the methane purity is greater than or equal to 90% VOL, the clean biogas is stored.

[0062] Exemplarily, the flow directions of the ammonia liquid in the permeate channel 22 and the biogas in the gas channel 31 are opposite, so that the ammonia liquid and the biogas are subjected to cross-flow absorption.

[0063] The relationship between the purity of methane in the clean biogas and the temperature difference between the two sides of the membrane module 23 and the biogas flow rate is as follows:

[0064] P=(0.5543+0.0054*T+0.001699*V)*100 Formula 1

[0065] Wherein, P is the methane content in the clean biogas, %; T is the temperature difference between the two sides of the membrane assembly 23, °C; V is the biogas flow rate, mL / min.

[0066] The ammonia concentration in the biogas slurry is closely related to the organic matter content in the sewage. For example, the ammonia concentration in the biogas slurry is 0.4-1 mol / L; the biogas slurry flow rate in the feed liquid channel 21 is 0.5-2 L / min.

[0067] The ammonia liquid circulates in the permeate channel 22, and the flow rate of the ammonia liquid is 0.5-2 L / min.

[0068] The CH4 concentration in biogas is closely related to the concentration of anaerobic bacteria and the anaerobic environment. For example, the methane concentration in biogas is 60% VOL.

[0069] The processing method of the integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation provided by the present invention is described below with reference to specific embodiments.

[0070] Example 1

[0071] This embodiment provides a treatment method for an integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation, using biogas slurry produced by a biological sewage treatment process in a sewage treatment plant as a feed liquid, wherein the ammonia concentration in the feed liquid is 0.6 mol / L, the methane concentration in the biogas is 60%VOL, and the carbon dioxide concentration is 40%VOL, and the method comprises the following steps:

[0072] S1. 1L of biogas slurry is heated to 70°C by a heating device 25 and fed into the feed liquid channel 21 of the direct contact membrane distillation structure, so that the temperature of the condensed water in the permeate channel 22 is constant at 10°C. Under the action of the vapor pressure difference, the water vapor and ammonia gas in the biogas slurry enter the permeate channel 22 and are enriched to form ammonia liquid; wherein the biogas slurry circulates in the feed liquid channel 21, and the flow rates of the biogas slurry and the condensed water are both 1L / min; the pore size of the membrane assembly 23 is 0.22μm;

[0073] S2, 5L of biogas is sent into the gas channel 31, so that the carbon dioxide in the biogas enters the permeate channel 22 through the microporous hollow fiber membrane 32, and the ammonia liquid in step S1 absorbs the carbon dioxide in the biogas; wherein the biogas flow rate is 100mL / min; the ammonia liquid and the biogas are cross-flow absorbed;

[0074] S3. Allow the biogas to circulate in the gas circulation treatment passage for 1 hour, and detect the methane content in the clean biogas.

[0075] Embodiment 2-6

[0076] Examples 2-6 respectively provide a treatment method for an integrated ammonia liquid recovery and carbon fixation system based on membrane distillation. Compared with Example 1, Example 2 only adjusts the biogas flow rate, and Examples 4-6 respectively adjust the biogas flow rate and feed liquid temperature accordingly. The rest is consistent with Example 1 and will not be repeated here.

[0077] Compared with Example 1, Example 3 only adjusts the biogas flow rate. The methane detection device 342 detects the time required for the methane content in the biogas to reach 90% VOL.

[0078] The parameter adjustments of Examples 2-6 are shown in Table 1.

[0079] Comparative Examples 1-3

[0080] Comparative Examples 1-3 respectively provide a treatment method for an integrated ammonia liquid recovery and carbon fixation system based on membrane distillation. Compared with Example 5, Comparative Example 1 reduces the biogas flow rate, and the rest is consistent with Example 5; compared with Example 6, Comparative Examples 2-3 respectively adjust the biogas flow rate, and the rest is consistent with Example 6.

[0081] The parameter adjustments of Comparative Examples 1-3 are shown in Table 1.

[0082] The detection results of the methane content in the clean biogas of Examples 1-6 and Comparative Examples 1-3 and the methane calculation results calculated using Formula 1 are shown in Table 1.

[0083] Table 1 Parameters and test and calculation results in Examples 1-6 and Comparative Examples 1-3

[0084]

[0085]

[0086] In Table 1, the methane detection content is the methane content in the clean biogas detected by gas chromatograph, the methane calculated content is the methane content in the clean biogas calculated by formula 1, and the calculation formula of the relative error is: relative error = |methane calculated content-methane detection content| / methane detection content.

[0087] As shown in Table 1, the relative errors between the calculated methane content and the detected methane content in Examples 1-2 and 4-6 are all less than 0.05, indicating that Formula 1 of the present invention can accurately reflect the relationship between the methane content in the clean biogas and the flow rate of the two sides of the membrane module and the biogas.

[0088] Compared with Example 1, in Example 2, when the temperature difference on both sides of the membrane assembly 23 and the treatment time remain unchanged and the biogas flow rate is increased from 10 mL / min to 50 mL / min, the methane content in the clean biogas increases by 7%. In Example 3, when the temperature difference on both sides of the membrane assembly 23 is 60°C and the biogas flow rate is 100 mL / min, the methane content in the clean biogas can reach 90% after 0.5 h, indicating that the treatment of carbon dioxide in biogas can be quickly completed by controlling the temperature difference on both sides of the membrane assembly 23 and the biogas flow rate.

[0089] Compared with Example 5, when the biogas flow rate was adjusted from 100 mL / min to 20 mL / min in Comparative Example 1, the methane content in the clean biogas was only 82% after 1 hour of treatment; compared with Example 6, when the biogas flow rate was adjusted from 100 mL / min to 10 and 50 mL / min in Comparative Examples 2 and 3, the methane content in the clean biogas was only 66% and 82% respectively after 1 hour of treatment; compared with Example 4, the biogas flow rate was the same in Comparative Example 3, and the only difference in the treatment part was that the temperature difference between the two sides of the membrane assembly 23 in Example 4 was 50°C, and the In Example 3, the temperature difference on both sides of the membrane assembly 23 is 30°C. After treatment for 1 hour, the methane content in the clean biogas of Example 4 is greater than 90%, while the methane content in the clean biogas of Comparative Example 3 is only 82%, indicating that the change in the temperature difference on both sides of the membrane assembly 23 and the biogas flow rate will significantly affect the methane content in the final clean biogas. By controlling the temperature difference on both sides of the membrane assembly 23 and the biogas flow rate to control the ammonia liquid enrichment rate and the carbon dioxide absorption rate, the carbon dioxide absorption efficiency can be maximized, thereby achieving the optimal economic benefit while rapidly reducing the carbon dioxide content in the biogas.

[0090] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. An integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation, characterized in that: include: A biogas slurry tank, used for storing biogas slurry; A direct contact membrane distillation structure, comprising a permeate channel, a feed liquid channel connected to the biogas slurry tank, and a membrane assembly arranged between the permeate channel and the feed liquid channel; Temperature control equipment, used to control the temperature difference on both sides of the membrane module; a gas channel, wherein a microporous hollow fiber membrane is disposed between the gas channel and the permeate channel, so that the gas channel, the microporous hollow fiber membrane and the permeate channel together form a gas separation structure that utilizes the liquid continuously enriched in the permeate channel as a carbon dioxide absorbent; A biogas tank connected to the gas channel; The methane detection device is used to detect the methane purity in the clean biogas output through the gas channel.

2. The integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 1, characterized in that: The permeate channel is provided with a first suction pump for circulating the liquid in the permeate channel.

3. The integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 1, characterized in that: The gas channel outlet is connected to its inlet to form a gas circulation processing passage.

4. The integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 1, characterized in that: The membrane assembly and the microporous hollow fiber membrane are both polytetrafluoroethylene membranes with a membrane pore size of 0.22-5 μm.

5. The integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 1, characterized in that: The temperature control device comprises a heating device for heating the biogas slurry and a cooling device for reducing the temperature of the permeate.

6. The processing method of the integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 1, characterized in that: The steps include: S1. The biogas slurry in the biogas slurry tank is fed into the feed liquid channel of the direct contact membrane distillation structure, so that under the action of the vapor pressure difference, the water vapor and ammonia gas in the biogas slurry pass through the membrane assembly into the permeate channel to be enriched to form ammonia liquid; S2, sending biogas into the gas channel, allowing carbon dioxide in the biogas to enter the permeate channel through the microporous hollow fiber membrane, and using the ammonia liquid in step S1 to absorb carbon dioxide in the biogas; S3, using a methane detection device to detect the methane purity in the clean biogas output from the gas output channel, and if the methane purity is less than a certain value, allowing the clean biogas to enter the gas channel again for processing; If the methane purity is greater than or equal to a certain value, the clean biogas is stored.

7. The treatment method of the integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 6, characterized in that: The flow directions of the ammonia liquid in the permeate channel and the biogas in the gas channel are opposite, so that the ammonia liquid and the biogas are subjected to cross-flow absorption.

8. The treatment method of the integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 6, characterized in that: The relationship between the purity of methane in the clean biogas and the temperature difference between the two sides of the membrane module and the biogas flow rate is as follows: P=(0.5543+0.0054*T+0.001699*V)*100 Wherein, P is the methane content in the clean biogas, %; T is the temperature difference between the two sides of the membrane module, ℃; V is the biogas flow rate, mL / min.

9. The treatment method of the integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 6, characterized in that: The ammonia concentration in the biogas slurry is 0.4-1 mol / L.

10. The treatment method of the integrated system for recovering ammonia liquid and fixing carbon based on membrane distillation according to claim 6, characterized in that: The ammonia liquid circulates in the permeate channel, and the flow rate of the ammonia liquid is 0.5-2 L / min.

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